The sweet potatoes in this pie originated in the New World. Photo: paul goyette.

As you fill your grocery cart with food for Thanksgiving, pause for a minute and think about where that food came from. I don’t mean is it local or organic or hormone/pesticide /gluten-free—I mean is it Old World or New World? On what continent did that food evolve?

During the age of exploration, Europe was called the Old World, along with its continental neighbors in the Eastern Hemisphere, Africa and Asia. The Americas, North and South, were the New World. Australia is sometimes lumped with the New World, too. This is a geographical and historical division. But the Old World/New World distinction also speaks to the biology of the regions. Organisms that originated on one continent are different from those that evolved halfway around the world. And for the most part, living things—animals, plants, microbes—didn’t travel from one hemisphere to the other without human help.

The sweet potato/yam mash-up is my favorite example of an Old World/New World confusion. Sweet potatoes originated in Central or South America, and are the starch-filled roots of plants related to morning glories. Yams, however, are completely different. They originated in Africa, and are actually the stem tissue of a monocot plant. Most of what we see labeled as “yams” in our grocery stores are actually sweet potatoes. The common name confusion started centuries ago, when African slaves brought the name—but not the vegetable—to the Americas with them. Yams don’t grow in temperate North America; they need a tropical climate, like Africa, Asia, or the Caribbean (where they’ve been imported).

So let’s go through your grocery cart. Your soon-to-be-mashed potatoes? New World—they originated in South America. (And the Irish Potato Famine occurred long after potatoes were imported to Europe.) The corn in your cornmeal stuffing originated in the New World, too. Your turkey is from the New World, but the soy in your tofurkey is native to Asia. And the apple in your apple pie is not at all American—it originated in Europe.

Many foods have moved across the ocean. This mixing of culinary components and cultures is definitely something to be thankful for. (Invasive plants and animals—and diseases—that have crisscrossed continents are something else entirely.) This Thanksgiving weekend, I plan to read the book 1493: Uncovering the New World Columbus Created. Author Charles C. Mann writes about the Columbian Exchange—the movement of plants, animals, and people from one hemisphere to the other. I’ll read it while enjoying a cup of coffee (Old World—Africa) and some leftover pecan pie (New World—North America).

<a title='By User:Nino Barbieri [CC-BY-SA-2.5 (www.creativecommons.org/licenses/by-sa/2.5)], from Wikimedia Commons' href='http://commons.wikimedia.org/wiki/File:-_Pumpkins_-.jpg'>By User: Nino Barbieri [CC-BY-SA-2.5], from Wikimedia Commons

I come from a family of chefs; I love to cook and during Thanksgiving I am happiest in the kitchen. I can be in a kitchen for hours on end amongst knifes, produce, herbs and sauces in the midst of creation. It usually takes me the whole day to create a meal my family can consume in fifteen minutes flat. But since I cook, they end up doing the dishes so it works out!

For the past several years, I’ve focused on really healthy meals and have become much more interested in the nutritional impact of food. The average Thanksgiving dinner has a whopping 3500 calories; it would take about 7 hours of moderate biking to burn off the whole meal. I skip the sweeter version of sweet potatoes. I serve baked rosemary sweet potato fries; I’ve also tried ginger and lime infused butternut squash soup, cabbage steamed with apples and tomatoes, polenta with herbs and a trio of mushrooms instead of stuffing and pumpkin pudding instead of the pie. For the past several years, I have also brined my turkey and then used the leftovers to make turkey stock and turkey soup.

Most of my favorite recipes have come from a medical focused cookbook called SuperFoods RX by Dr. Stephen J. Pratt & Kathy Matthews. This book outlines the health benefits of fourteen powerhouse foods that aid in health and longevity in life. Four prominent Thanksgiving food items make the list:

Turkey – Turkey is in itself is a lean source of protein, but it also packs nutrients like Riboflavin, Niacin, Iron, Selenium, Zinc, Vitamin B6 and Vitamin B12. Eating turkey is good for your heart and also lowers the risk for cancer.

Pumpkin – This fruit is part of the gourd family (the same family that incorporates melons) and is very high in fiber and low in calories. It has a great deal of nutrients like potassium, pantothenic acid, magnesium, and vitamins C and E. It also has high concentrations of digestable carotenoids specifically alpha-carotene and beta-carotene. Carotenoids are linked to decreasing the risk of many cancers and women who have the highest dietary concentrations of cartenoids also have the lowest risk of breast cancer. These nutrients also lower the risk of heart disease as well as the risk for cataracts.

Sweet Potatoes – The sweet potato is a sidekick to pumpkin and has many of the same nutrients and health benefits.

Cranberries – Cranberries are a sidekick and cousins to Blueberries; both Cranberries and Blueberries are native to North America. These small berries have very high levels of antioxidant phytonutrients. Phytonutrients have been shown to aid in body cells communicating efficiently even aiding aging brain cells from further degeneration, preventing cellular level mutations, and fighting the onslaught of cancer cells.

Many of my recipes and health insights have come from this book. I have a very dog-eared and tattered copy of it on my kitchen shelf. To find more about these superfoods and the rest of the list go to the Superfoods RX website.

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A wild turkey, on display for the local ladies. Photo: Alan Vernon.

As Thanksgiving approaches, all thoughts turn to turkeys. Especially when I see a gang of wild ones impeding my progress as I walk to my office in the Berkeley hills. These turkeys are feathered and feisty, strutting on their skinny legs and poking the ground with their sharp beaks.

Wild turkeys, Meleagris gallopavo, are not native to California. They were first introduced to the state for hunting in the 1870s. Subsequent introductions, in the 1920s and 1950s, failed to take—the birds were farm-raised and they didn’t fare well. In the 1970s, California Fish and Game introduced a subspecies called Rio Grande (M. gallopavo intermedia), wild-caught from Texas. This time, the turkeys kept trotting.

Fish and Game estimates that there are now 240,000 wild turkeys in California. Some think of wild turkeys as dinner—you can hunt them, if you have a license. One of my students assures me that they are delicious. However, others think of them as pests. People blame them for digging up gardens, leaving droppings, and scratching cars (especially if a turkey sees his reflection in a shiny car door). To prevent turkeys from damaging your property, California Fish and Game has some recommendations in their Keep Me Wild guide.

Like the feral pig, another non-native species that was introduce for hunting, wild turkeys have important effects on our local ecosystems. Turkeys tear up the ground in their search for tasty insects. They eat a wide variety of foods, from acorns to lizards. Daniel Gluesenkamp at the Audubon Canyon Ranch studied their ecological effects. Check out this article from Bay Nature to learn more.

I used to think of turkeys as the Norman Rockwell Thanksgiving Dinner archetype: plucked, basted, and golden brown. But now that I’ve seen wild turkeys, I have much more respect for these birds. They are proud, regal, and frankly a bit intimidating. I now understand why Ben Franklin wished the Founding Fathers had chosen the turkey, rather than the bald eagle, as the nation’s bird.

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Brining a turkey can help retain more moisture and flavor during the cooking process. Photo by Shawn Hatfield.

I grew up in a family of chefs. I think I was three when I cooked my first meal on our olive green gas stove. My brother proudly watched over my process as I burned scrambled eggs. Since then, my abilities have improved. Thanksgiving is one of my favorite holidays because I get to be in the kitchen for a good solid chunk of time. For those who love to cook, Thanksgiving is like the SuperBowl.

For the last couple of years, I have brined the bird. One of the things I hated growing up at Thanksgiving was overcooked turkey. It is dry, flavorless and feels like eating cardboard. I would often forgo turkey because of how dry it was. Meat, especially lean meat like turkey loses about a third of its moisture during cooking. One year, my uncle tried to alleviate this dryness by deep fat frying the turkey. However, he forgot to heat the oil before putting the bird in the cooker which is a fairly big no-no. Needless to say that year, I was very grateful that I was a practicing vegetarian.

Brining has been my preference for the past three years because it is far healthier than deep fat frying and it cuts the cooking time in half. Most importantly is creates a juicy delicious Thanksgiving turkey. Brining entails soaking the meat for a number of hours in a chilled solution of salt and water. I got my recipe off the food network site, specifically from Alton Brown on Good Eats and it includes salt, vegetable stock, brown sugar and various spices.

But how does brining work? The salt solution passes through the permeable meat cells during the soaking process using the method of osmosis. Osmosis is the diffusion of water through a semi-permeable membrane – in this case the meat cells. Through diffusion, the salt and water within the meat cells balance with the salt and water in the surrounding brine which results in a higher concentration of salt and water in the meat. Food chemists disagree about the mechanics of this diffusion and how salt travels across membranes, but at the end of the day, the diffusion results in more water and flavor within the cells of the meat.

The high concentration of salt also denatures protein strands. In their normal state, the strands are tightly wound; denatured strands unwind and tangle. During cooking, this unusual structure traps water molecules and holds onto them. The end result of this osmosis is less moisture is lost during cooking. This year, I couldn’t cook on Thanksgiving day so I invited friends over for pre-Thanksgiving. The turkey turned out just as good as last year. Even the leftover bird was moist after being reheated in a microwave. Which means that this is a recipe that will stay in the folder in my kitchen for years to come…

Happy Thanksgiving!

For more information about the science behind cooking, here are some great websites:

Cooking for Engineers
Exploratorium’s Science of Cooking
Good Eats on the Food Network

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Turkey cannot be the only culprit of induced drowsiness after
a Thanksgiving meal.

Tryptophan is an essential amino acid. An essential amino acid is one that our bodies cannot synthesize, so it must come from food or supplements. Tryptophan is not only a building block in protein biosynthesis in our body but also a biochemical precursor for synthesizing Serotonin, Melatonin and Niacin. Both Serotonin and Melatonin are factors in inducing drowsiness and sleep. Serotonin is a neurotransmitter that facilitates emotions including desire, body temperature, sleep, appetite and metabolism. Serotonin can also be converted into Melatonin, which further regulates sleep, maintaining the circadian rhythms of several biological functions.

The foods that contain Tryptophan are usually protein-based and include chocolate, oats, milk, yogurt, cottage cheese, red meat, poultry, fish, eggs, along with specific nuts and certain fruits. However, turkey contains the same amount of Tryptophan of other meats. Most meats contain .25 grams of Tryptophan per 100 grams of food while dried egg whites contain 1 gram of Tryptophan per 100 grams of food. Turkey cannot be the only culprit of induced drowsiness after a Thanksgiving meal. If this was indeed true, people would be drowsy after any normal meal containing meat as the levels of Tryptophan are equivalent.

The other two denominators with the Thanksgiving meal are high carbohydrates and fat. An average Thanksgiving meal can have 3000 calories and 239 grams of fat. In comparison, United Nations FAO says the average American consumed 3770 calories per day in 2001-2003. It has been shown in studies in both animals and humans that a meal high in carbohydrates and fat triggers Insulin. Insulin them stimulates the uptake of large neutral branched-chain amino acids, known as LNAA.

Tryptophan does not fall into the LNAA family and thus the ratio of Tryptophan to LNAA in the blood stream increases when Insulin is released into the blood stream. Less competition for transporters in the blood stream results in the uptake of Tryptophan across the blood-brain barrier and the synthesis of Serotonin and Melatonin. This in turn creates the lethargy and drowsiness common after the Thanksgiving meal. Therefore it is not turkey alone that ends in a nap after Thanksgiving dinner. It is a collaborative process. Without the intake of carbohydrates dressed up as rolls, sweet potatoes, mashed potatoes, stuffing and pumpkin pie, the Tryptophan in the iconic Thanksgiving turkey would have too much competition for synthesis. Insulin clears away the competition and in turn isolates Tryptophan in the blood stream enabling it to be readily synthesized. The whole meal is responsible for the drowsiness. The next question that could be posed is this the body’s way to have us slow down to aid digestion?

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